


Barnacles and Biscuits

by thedeadguyintheback



Category: Sherlock (TV)
Genre: M/M, Mpreg, Sherlock AU, mermaid au
Language: English
Status: Completed
Published: 2014-02-07
Updated: 2014-02-07
Packaged: 2018-01-11 11:24:18
Rating: Explicit
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 4,502
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1172471
Author URL: https://archiveofourown.org/users/thedeadguyintheback/pseuds/thedeadguyintheback
Summary: <blockquote class="userstuff">
              <p>merlock au. that should tell you pretty much everything.<br/>Captain John Watson returns from the war, only to make an exciting discovery off the starboard side of his little fishing boat, the Mary Morstan.</p>
            </blockquote>





	Barnacles and Biscuits

**Author's Note:**

> forgive me, i'm shitty at titles. and everything else, too.

Captain John Watson was not what one would expect when someone said ‘Captain.’ He was not a great fearless leader, or a dashing seaman eager for adventures on distant shores. He was a simple man of meager means, and preferred his fishing boat to any grand mansion. He preferred to avoid loud clubs and parties in favor of a quiet cup of tea on the dock.

On this particular morning, Captain Watson had just returned from serving his time in Her Majesty’s Armed Forces. It had been several years, he realised, since he’d last seen Pembroke dock and beheld the familiar sight of his old boat bobbing in St. George’s Channel. He sighed with relief as he finally found the Mary Morstan floating between the larger vessels. His sister had kept her word about keeping it safe while he was gone.

Just as the sun began to peek above the horizon, he began making her ready to sail. Mary was just a small fishing boat, so John could sail her all by himself without any need to hire a crew. Together the two of them made their way out of the channel and into the open ocean. John breathed in the salted air as he examined the skies with a careful eye. He was finally home.

But something wasn’t right. As familiar as it all was, the spray of the sea, the rocking of the boat underneath his feet, the sound of waves lapping against the boat… It just wasn’t the same to John. He was too distracted by the war still playing in his head like a waking nightmare. He couldn’t shut out the visions of all those poor men dying under his hands. He couldn’t ignore the sound of gunfire that he knew didn’t exist. He couldn’t get the scent of charred flesh from his nose. It all lingered at the back of his mind, keeping him from enjoying the one thing he had longed for all those years away.

As he stared over the gunwale at the dark blue waters below, horrible ideas began to take hold. He could make the war stop… He could make it all go away. It wouldn’t even be painful. Before he could weigh the decision logically, John found himself sinking slowly into the ocean.

Part of him liked the feel of the cold ocean around him, the push and pull of the waves against his body. It was all very peaceful, and entirely un-warlike. Another part told him that this was insane, that there was no reason to be doing this. But no matter how loudly that part of him screamed, his arms and legs wouldn’t listen.

Then, just as all of him seemed resigned to this final fate, something began to swim towards him out of the gloom. A dolphin? A shark? It seemed to move like one, but its shape was entirely wrong. And did it have arms? It couldn’t be…

It was. John watched with interest as the figure swam up close to him, half man and half fish. The merman regarded him with curious eyes, then looked up at the boat looming above them. Then he seemed to come to some conclusion.

John looked on as the merman swam quickly up to the surface, returning with an eager expression. Holding John’s face gently, he kissed the captain softly, providing him with a lungful of air. John hadn’t realised until now how his lungs were burning, and this first breath felt like a cool wave on the sudden fire. Then the mysterious benefactor pulled him upward to the surface, where John began gasping and coughing while he scrambled for a handhold on the side of the boat.

Turning to the merman, he said after regaining his breath, “You saved me.”

The merman smiled, rolling his eyes sarcastically. “What was I supposed to do, stand by and let you commit suicide?”

John did a double take. “You can speak!” Then he added, “How did you know I was trying to kill myself?”

“Obvious, really; I gathered the facts and made a deduction. Your vessel is small, not built for carrying passengers. That and your clothes say that you’re an experienced sailor. Any sailor would at least be able to swim, but you weren’t even making an effort. You were conscious, and under for more than three minutes, ruling out the option of a recreational swim. Ergo, attempted suicide. Am I wrong?”

John sat, dumbfounded. “No, no you’re not.”

The merman nodded. “So, Afghanistan or Iraq?”

“I’m sorry?”

The merman rolled his eyes, clearly becoming bored. “I recognized the bottom of your boat. You frequented this area south of Pembroke for many years, then you abruptly stopped. Your three-year absence and the tired look in your eyes says you were gone to serve in the military; the tanned quality of your face and the sand washing out of your clothes says somewhere very sunny and desert-like. So, Afghanistan or Iraq?”

John couldn’t help but smile. “Afghanistan! That’s amazing!”

The merman tried to seem unperturbed, but John could see a hint of a smile tugging at the edge of his mouth as he retorted, “Meretricious.”

The captain laughed, and the merman laughed with him. “So, mister mysterious lifeguard, do you have a name?”

“Sherlock. Can I visit you at the dock sometime?”

“Sure. The name’s John Watson and the address is 221B Pembroke Dock, the Mary Morstan.”

… … …

It was bright and early the next morning when John heard a rapping on Mary’s hull. He forced himself sleepily from his hammock and up the stairs to the deck. Looking over the gunwale, he found Sherlock making impatient figure-eights in the water. “Don’t mermaids sleep?” he asked, rubbing the sleep from his eyes.

“Of course, John. What a silly question!”

After a pause, John shrugged. “Alright. I’m gonna make some tea. Would you like some?” He turned and went downstairs to turn on the kettle. He called back over his shoulder, “Do mermaids even drink tea?” Rather than a response, he felt the boat dip unexpectedly to one side as Sherlock pulled himself onto the deck.

“Honestly, I’ve never had proper tea. Is it commonplace on land?”

“Very.” John bustled about the tiny kitchen, while Sherlock watched intently from the deck outside. “I suppose you could say it’s the staple beverage of the British Isles. Biscuit?”

“What?”

“Oh, it’s uhh—ʺJohn said as he went about making the tea. “It’s food.” He handed a cup of tea and a biscuit to Sherlock, who sat between the gunwale gap with his fluke hanging down into the water. “Try it; I think you’ll like it.” John sat next to him on the gunwale, and watched curiously while Sherlock sampled the unfamiliar fare. “Just out of curiosity, what is your normal diet?”

“Primarily krill, small fish, and several varieties of algae and seaweed.” Sherlock said matter-of-factly, as if he got asked this question all the time. “And yours?”

“Mostly tea and biscuits,” John replied with a laugh. “Though, most humans have a much more varied diet, ranging from meats and plants to grains and animal byproducts.” Sherlock nodded; undoubtedly he’d already known the answer, and was just making polite conversation. Based on yesterday’s events, John was willing to bet that this merman knew a lot more than he let on. “So, I’m guessing by the fact that you’re not currently gasping for oxygen that you’re okay on land? I mean, you’re not gonna start asphyxiating in the next few minutes, are you?”

“Hardly. I have lungs.”

After a pregnant pause, John ventured to ask, “Mind if I have a listen?”

… … …

“I’m an adult male of my species, 35 years of age.” Sherlock stated, and John might have said he was bragging the way he stated it. “rather long for an average merfolk, at almost 183cm—ʺ

John scribbled furiously in a plain looking notebook, copying everything Sherlock offered, and adding his own notes here and there. On one page was a list of medical information ranging from eye color to heart rate and blood pressure. On the opposite page was a detailed diagram of Sherlock’s muscular and skeletal structure, complete with labeled bones and muscle groups. “So, from the looks of it, your anatomical structure is very close to that of a dolphin. You say you’re a mammal—” John mumbled to himself as he continued scribbling in the notebook. “Your heart rate is incredibly low. How much oxygen can your lungs hold?”

“About five liters.”

“That’s incredible! How long can you stay submerged before you have to resurface for air?”

Sherlock looked perturbed. “Honestly, I never timed it before.” He dove into the water with an unceremonious “Be right back.”

It took a while. John leaned against the gunwale gap, tapping his pencil against the notebook’s pages, scribbling another note here or there. Sherlock finally resurfaced with a loud gasp of air. “Bloody hell, that was almost 45 minutes!” John announced after double checking his watch. “How fast can you swim?”

… … …

“How come humans think merpeople are just a myth?”

“Any human who managed a good look at a merfolk usually went blabbing to their mates and was immediately labeled as a raving lunatic.” Sherlock explained matter-of-factly. “Half man, half fish? Honestly! There are far more credible ways of describing a merperson than that.”

John shrugged. “Then why do merpeople hide from us? I mean, you’re not deep-water dwellers; you usually live around coral reefs. Clearly the merfolk are hiding from humans, or you’d be seen a lot more often.”

“Merfolk have learned to stay away from humans, on pain of death.” Sherlock said dryly. “Among merfolk society, contact with the human world is forbidden, for fear of the entire race being found and wiped out for sport. I, on the other hand, was far too curious to stay away…” He nibbled a biscuit pensively. “And besides—ʺ

“Besides, what?”

“Oh… Nothing.”

… … …

It was an average day on the Mary Morstan. Sherlock was imparting to John a study that he’d conducted, pertaining to the different species of algae and barnacles that grew on ships from different regions. “So,” John said with playful skepticism. “You can look at the bottom of any boat here, and tell me where it’s been?”

Sherlock started to explain further, but turned suddenly at the sound of footsteps approaching on the dock. “Get in the water,” John commanded quite unexpectedly. “Stay out of sight until I come get you.” Sherlock didn’t waste time questioning John’s sudden ferocity, disappearing into the water without so much as a nod.

John busied himself with the ropes on the boom, watching nonchalantly as the footsteps drew nearer. Two men in suits walked slowly down the docks, examining the larger ships and discussing. They paused to inspect a ship next to the Mary Morstan, and John eyed them discreetly as he retied a knot here or there. Finally, they moved on.

Leaning over the bow gunwale, John found Sherlock clinging to the keel just below the water’s surface. “All clear, you can come up.”

“Who were they?”

“Business men, probably investors,” John said. “Not sure why they were inspecting the vessels personally… but they definitely didn’t need to see you.” Sherlock only nodded in agreement.

… … …

“Are you alright, Sherlock?”

“Hmm? Oh, yes. Yes, I’m fine.”

“You sure? You seem a bit distracted…”

The two of them sat in heavy silence on the deck of the Mary Morstan, floating calmly in international waters. It was a while before Sherlock finally spoke up. “John, I want to show you something… but you have to promise me something.”

“Anything.”

“You have to promise me that you won’t tell another living soul about it, as long as you live.”

John raised his right hand ceremoniously. “You have my word as a friend that I will never tell another living soul about you, your people, or anything you show me.”

Sherlock nodded, satisfied. “We’ll have to go after nightfall, if that’s alright. And it’ll require some swimming on your part; it’s not accessible by boat.”

“That’s fine,” John assured him. “It’s all fine.”

As the day progressed, Sherlock seemed to get increasingly restless and distracted. When the sun started to sink below the ocean, he hung on the gunwale and began giving John specific instructions. “—sure to come around the south side of the island, and don’t weigh anchor until I’ve signaled you. Have you got all that?”

“Yes, I’ve got it. Sherlock, what’s all this about?”

“I’ll see you tonight.” Sherlock said before he leaned up and placed a single chaste kiss on John’s lips. Then he disappeared into the dark waves, leaving John dumbstruck.

… … …

Long after nightfall, the Mary Morstan quietly approached a small island far from the coast, approaching from the south side as instructed. From what John could see by the quarter moon, the island was fairly round and about a mile in diameter. As he waited, John noticed something that splashed quietly several yards off the bow, then again a few yards closer. Straining to see through the darkness, he could barely make out the dark head of hair that appeared on his port side.

“It’s me, John,” Sherlock said in a frantic whisper. “Weigh anchor, and get ready to swim.” John stripped down to his trousers and, after ensuring that there was nothing in his pockets, dove into the chilly waters. Before he had even come up from the plunge, he felt a hand in his.

Sherlock led him around the shore to the north side of the island. John had previously considered himself an avid swimmer, but Sherlock frequently had to wait for him to catch up nonetheless. But they eventually arrived at the north side of the island, where they found a small break in the wall only a few feet wide.

Inside, it appeared that the island was actually a caldera, filled in with a considerable coral reef almost a mile wide. John noticed that the water inside the caldera was considerably warmer than that outside. “This is beautiful, Sherlock!” John said, scrambling clumsily onto a small island of sediment so as to get a better look at the surrounding coral reef. “It’s amazing!”

“It’s more than just that,” Sherlock explained from the water below him. “This is the breeding ground for merfolk.”

“Wow,” John whispered in a suddenly more reverent voice.

“That’s why we had to come at night. If anyone saw you here…”

“You’d be shunned, persecuted, and probably banished. Right?” He smiled knowingly, and Sherlock smiled back. “It’s okay, Sherlock. I understand.”

Sherlock took a few deep, shaky breaths before speaking again. “John, I brought you here for a reason.” Before he could continue, John knelt down to his level.

“I know.”

Grasping both sides of Sherlock’s face, he planted a firm kiss on his soft lips. Sherlock all but collapsed into the water, and sat gaping after John had released his grip. “How did you—ʺ

“Easy,” John replied with a wink. “I gathered the facts and made a deduction.” He tackled Sherlock playfully, and the two went tumbling into the water. Sherlock began turning circles around John, suddenly quite elated. He tried to pull John into deeper waters, but John resisted. Surfacing, he reminded Sherlock between gasps, “I still have to breathe.”

“As do I,” Sherlock said as he slipped into a fit of giggles. “but you humans require so much oxygen that it’s pathetic.” John kissed him quiet, and they sank back into the still blue waters, wrapped around one another. Sherlock guided them gracefully to a small bank, nestling himself into the coarse sediment. John crawled over him, effectively pinning Sherlock without actually touching him. They explored each other’s faces, lips, mouth. John’s hands began to follow suit, quietly noting what elicited the most vocal responses from Sherlock. The merman, in retaliation, delved his hands into John’s trousers, removing them in one swift maneuver. Then, he buried the fingers of one hand in John’s short locks, placing the other on his lower back and pulling him closer.

“Tell me what you want, Sherlock,” John whispered into his ear. “Tell me what you want me to do.” He got only a whimper in response, which simply wouldn’t do. “Sherlock, I’ve never done this. You’re going to have to help me.”

At that, a hand was on his, and Sherlock guided him to an almost indiscernible slit below his pelvis. “Here,” he whispered into John’s neck, caressing himself under John’s fingers. “Just there. Please, John…”

John wordlessly obliged, pressing himself slowly in. “Is that alright?” he asked nervously. “Does it hurt?” Taking Sherlock’s silence as a ‘no,’ he pushed further in, and slowly began moving his hips in tandem with Sherlock’s ragged breathing. He, in turn, laced his fingers behind John’s neck, pulling him into a deep kiss that followed the rhythm of their bodies.

… … …

After that night, it was a while before Sherlock returned to Pembroke Dock. The time John didn’t spend on shore working for spare change was filled in sitting at the bow of the Mary Morstan, watching the waves for a familiar head of dark hair. On one particular day, a new ship had docked next to Mary, a whaling vessel from somewhere far off. The crewmen spent most of the day drinking and shouting at one another, and John grew quite tired of it.

It was just before sunset when he first spotted Sherlock way off. Someone shouted indiscernibly on the whaling boat. Sherlock surfaced again a bit closer, eyeing this new vessel warily. Someone else shouted on the boat, and one phrase was clearly discerned: “There it is again!”

John anticipated the next thing to happen, but only a split second in advance. He could only watch in horror as a small harpoon flew into the water, just where Sherlock had been a split second before. A small plume of red rose to the surface, but no Sherlock. Another harpoon was readied.

“Don’t you dare!” John shouted before diving into the water. He didn’t stay to ensure the men listened, but he didn’t get hit with a harpoon, so it must have worked.

It only took a moment of searching to find Sherlock steadily sinking into the gloom, with a harpoon piercing his lower left side, just above what John would consider his knee. He was conscious, but was struggling to swim with the harpoon restricting his movements. And he was bleeding heavily, John noticed with dread.

John made his way to Sherlock, hoping his fear didn’t show on his face. After wrapping his arms securely around Sherlock’s midsection, he started upwards, aiming between the vessels. His lungs burned for air, and he stubbornly ignored them. As the pair finally surfaced, John’s first breath of air went instantly into shouting a blue streak of vulgar threats at the men on the whaling ship.

Sherlock was beginning to go limp in his arms, John realized with horror. Struggling, he swam quickly to the other side of the Mary Morstan away from the whaling vessel, at least as quickly as he could with a dying man in one arm. After fervently praying that no one would notice Sherlock’s fluke, John climbed onto the boat, pulling Sherlock up after him. Then, before anyone could get a good look, he whisked the bleeding merman into the galley, slamming the door behind him.

He laid Sherlock on the floor, avoiding the harpoon as best he could, since there wasn’t a table big enough to hold him. Leaning over his limp form, John whispered desperately into his ear, hoping that he would hear.

“Please don’t die.”

… … …

John sat on a stool, head in his hands. Sherlock lay in the hammock, a blood-stained sheet covering most of him. The galley was eerily quiet but for his own breathing, until John was pulled from his reverie by a quiet knock on the galley door. The curtain had been pulled over the porthole, so John ensured that the sheet hid all of Sherlock’s inhuman half before leaving the galley.

Standing on the deck were three men in ragged clothing. One of them spoke, John recognizing the accent from the whaling vessel. “We wanted to see how he was doing, after what happened yesterday…”

“After you harpooned a man through the leg? Let’s run one through you, see how you hold up.” John did little to restrain his anger, arms folded to keep his fists in check.

The man looked sheepish, as if he couldn’t believe what he was about to say. “I thought… I thought he was a mermaid.”

John did his best to look incredulous, which didn’t take much effort at this point. “Bloody brilliant observation, mate. I decide to go swimming, are you gonna harpoon me as well?”

The first man stared at the deck in embarrassment, but a younger one didn’t appear to have grasped the situation properly when he asked, “Can we see him?”

“No, you bloody well can’t see him!” John snapped. “This galley is a sterile environment. I’m not allowing the likes of you to come in and muck it all up.” He pointed decidedly at the whaling ship. “Now get off my deck before I start throwing harpoons.”

He waited until the men were safely back on their own boat before returning quickly to Sherlock’s side.

… … …

Sherlock came sluggishly back to consciousness, vaguely aware of the sensation of water being poured gently over him.

“John?”

“Yeah, Sherlock, it’s me. I’m here.”

Sherlock tried to sit up, only to find that this was a difficult feat in a hammock. “It hurts…”

Gentle (and wet) hands pushed him back down. “You got a harpoon through your biceps caudalis. I’d be worried if it didn’t hurt.” John was sitting on a stool beside him, with what appeared to be a bucket of sea water. “Lie down, you need to rest.” He continued rubbing Sherlock’s smooth flesh with wet hands. John was keeping him hydrated, he realized. How long had he been asleep?

“Those men—ʺ

“Are long gone, and thoroughly convinced that you’re human.” He busied himself checking Sherlock’s bandages. “No worries. Your secret’s safe with me.”

“John, I—ʺ

“Relax, Sherlock. But if you’re not gonna sleep, then you may as well eat something. Feel up for it?” Sherlock only nodded in response. John didn’t allow any more talking until Sherlock had finished a bowl of stew, though that wasn’t to say Sherlock didn’t try.

“John,” he began after finishing, “I have to tell you something.” He felt a hand in his, which he placed gently on his belly, palm down. The pair stayed that way for a while, before John seemed to come to a conclusion.

“Sherlock… do you mean you’re—ʺ

“Yes.”

“… Is it mine?”

“Yes.”

There was a long silence between them, broken only by the waves slapping gently against the hull. “Bloody, hell… How? We’re not even the same species.”

Sherlock shook his head. “Quite frankly, it’s never been attempted. You know as well as I how this may turn out.” 

The silence began to return, until John started quietly laughing. Leaning over, he kissed Sherlock softly and stayed there, shoulders still shaking. “Don’t look so worried, love. Whatever happens, it doesn’t matter.” Another kiss. “None of it matters.”

… … …

Sherlock woke again, this time with the gentle weight of John’s head on his stomach. Noticing his even breathing, Sherlock decided not to wake him, choosing instead to study the shelf on the opposite wall filled with odds and ends. A long while later, he felt John stir, blinking the sleep from his eyes. “Oh, you’re awake already,” John said, the sleep quickly disappearing from his face.

Sherlock only nodded in response. “What’s that thing on the second shelf?” John looked in the direction he indicated. “The metal thing with the red bulb at one end. What is it?”

“It’s an antique oxygen tank. These days, they’re much bigger and come with lots of gauges and plastic tubing.” John explained.

Sherlock waited a while longer before asking the question that had been occupying his brain since he’d first awoken. “How am I alive? I should have bled out in the harbour, yet here I am. How?”

“You honestly don’t know?” John said with a chuckle. “I’m a doctor. Retired surgeon, actually. Surprised you never deduced that about me, with that brain of yours.” He laid a gentle hand on Sherlock’s midsection. “Why do you think I was so curious about your anatomy when I first met you?”

Sherlock frowned. “I assumed you were curious, like me.”

“No,” John said with a soft chuckle. “because you were curious. I knew it was only a matter of time before you got into something dangerous. And I was right.”

… … …

“So how did it actually happen?”

Sherlock hung an arm over the gunwale to look at John. It was still in the wee hours of the morning, so Pembroke dock was quiet and empty of even the calling of seagulls. “How did what happen?”

John pointed to Sherlock’s partially distended abdomen. “That. I mean, you told me the first time you visited that you’re an adult male. That being said, it doesn’t seem biologically possible.”

That had already crossed Sherlock’s mind. “Merpeople are born hermaphroditic, possessing both sperm and egg. The dominant gender develops later in life, but we remain in possession of both reproductive methods. Typically the recessive gender remains dormant, but our bodies are actually capable of changing gender in times of desperation, a survival tactic stemming from drastically low numbers.”

John held his chin in mock consideration. “Interesting,” he said teasingly, “but I think further experimentation is required.” He rolled over the gunwale and tackled Sherlock where he floated.

… … …

John returned to the caldera months later, in the silent hours of the night. He weighed anchor on the south side, then dove into the chilly autumn waters and made his way to the opening on the north side. There, he found Sherlock almost immediately, curled up on his side in a shallow eddy. “I’m here, love,” he said, trying very hard to keep the worry from his voice.

“The contractions have already started,” Sherlock said between ragged breaths.

John could do nothing but whisper assurances, putting his arms around Sherlock’s shoulders. They were unsure how the baby would react to pain medication, so it was best to just let it happen on its own. The hours passed at a near stand-still, Sherlock groaning with each new contraction and John whispering encouragement in his ear.

Finally, the ordeal was over. John held the squirming infant in gentle hands, holding him up for Sherlock to see. He was mostly human, with legs and feet, but with the addition of partially webbed fingers. "He's beautiful," John murmured. “What should we call him?”

“Hamish,” Sherlock replied sleepily. “John Hamish Holmes.”

“Alright,” John said, settling in beside him. “But if we have another, we’re naming it after someone in your family.”

**Author's Note:**

> i had some people ask me for more details on the reproductive anatomy of merpeople. all i can say is, think seahorses.


End file.
